An important step in the development of a film processor is determining the film characteristics after exposure and the type of toner to be used, i.e. liquid or power.
A large number of toner device designs for developing latent, electrostatic images exist; a few of these being disclosed in U.S. Pat. Nos. 3,202,526; 3,203,395; 3,627,410 and 3,651,782.
The basic principle involved in many toner apparatus is to place the electrostatically-imaged dielectric sheet in proximity to a developing electrode surface. Simultaneously, toner fluid is circulated across the dielectric sheet, to cause the pigment particles of the fluid to adhere to the electrostatically-charged image areas. Thereafter, the dielectric sheet is dried, to permit a binder agent such as a resin to cause the pigment to permanently adhere to the dielectric sheet.
Significant problems have existed in the prior art, which have restricted the utility of fluid toner devices as a means of developing dielectric sheets having latent electrostatic images. First, during the development process, the electrostatic sheet is desirably precisely and uniformly spaced from the developing electrode, yet with room for toner solution to circulate between the dielectric sheet and the developing electrode surface. Generally, the prior art has not provided a satisfactory solution for accomplishing this.
Also, the toner solution in use is quickly depleted of pigment particles. If the spent toner solution is permitted to continue to circulate in the presence of the electrostatic image on the dielectric sheet, it will begin to wash away pigment particles which have already been deposited on the electrostatic image, resulting in a poor, scratched, or smeared image on the dielectric sheet.
In accordance with this invention, the above problems are effectively eliminated resulting in toner a apparatus which can reliably provide uniformly-toned electrostatic images.